Acetone In Air Research Articles

Pore-Wall Chemistry and Photocatalytic Activity of Mesoporous Titania Molecular Sieve Films

Transparent zeolite-like mesoporous TiO2 nanocrystalline thin films with high photocatalytic activity were synthesized via a surfactant-templated method. The films were characterized by TGA−DTA, XRD, nitrogen adsorption, SEM, TEM, UV/vis, and FT-IR spectroscopy. The photocatalytic activity of the films was evaluated by photodecomposition of acetone in air at ambient conditions. It was found that thermal treatment resulted in surfactant elimination, framework solidification, as well as pore-wall crystallization of the mesoporous TiO2. The resulting zeolite-like mesoporous TiO2 nanocrystalline films had large specific surface areas (∼100 m2/g), high porosity (∼40%), extended band gap energy (∼3.3 eV), tri-directional communicating pore systems, and enhanced photocatalytic activity. The optimum calcination temperature was found to be 500 °C, at which the film possessed a cubic ordered mesoporous structure and exhibited the highest photocatalytic activity. A comparison with a conventional TiO2 film (prepared from a sol−gel method) showed that the ordered mesoporous TiO2 nanocrystalline film (calcined at 500 °C) had over 2 times the specific photocatalytic activity as the conventional film. The high photocatalytic activity of zeolite-like mesoporous TiO2 thin films can be explained by the large specific surface area and the three-dimensionally connected mesoporous architecture.

Low Temperature Solvent Evaporation‐induced Crystallization Synthesis of Nanocrystalline TiO2 Photocatalyst

AbstractA novel and efficient methodology for obtaining highly active photocatalyst of bi‐phase TiO2 with small particle size and high specific surface area was developed by solvent evaporation‐induced crystallization (SEIC) method at low temperature. The prepared TiO2 powder was characterized with X‐ray diffraction (XRD), transmission electron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the photocatalytic activity of the TiO2 powder prepared by this method approached that of Degussa P25. This may be attributed to the fact that the prepared TIO2 powder had larger specific surface areas (265 nr2. g−1) and smaller crystallite size (about 5 nm), but relatively low crystallinity, as compared with Degussa P25.

Effects of acidic and basic hydrolysis catalysts on the photocatalytic activity and microstructures of bimodal mesoporous titania

Bimodal mesoporous titania powders with high photocatalytic activity were prepared by hydrolysis of titanium tetraisopropoxide in the presence of HNO 3 or NH 4OH under ultrasonic irradiation. The powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface areas, and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The effects of catalysts added during hydrolysis on the microstructure and photocatalytic activity of the TiO 2 powders were investigated. The results showed that HNO 3 enhanced the growth of brookite, while NH 4OH not only retarded phase transformation of the TiO 2 powders from amorphous to anatase and anatase to rutile but also suppressed the growth of brookite. All TiO 2 powders calcined from 400 to 600 °C showed bimodal pore-size distributions in the mesoporous region: one was intraaggregated pores with maximum pore diameters of ca. 4–9 nm and the other interaggregated ones with maximum pore diameters of ca. 35–50 nm. At 700 °C, the pore-size distributions of all samples exhibited monomodal distribution of the interaggregated pores due to the collapse of the intraaggregated pores. The photocatalytic activity of the TiO 2 powders prepared by this method and calcined at 400 °C exceeded that of Degussa P-25 when the molar ratio of HNO 3 or NH 4OH to H 2O was less than 0.05.

Effects of Trifluoroacetic Acid Modification on the Surface Microstructures and Photocatalytic Activity of Mesoporous TiO2 Thin Films

Enhancement of the photocatalytic activity of sol−gel-derived TiO2 thin films by a simple treatment with trifluoroacetic acid (TFA) was investigated. The thin films were characterized with N2 adsorption, Fourier transform infrared spectroscopy, UV−visible spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, X-ray diffraction, atomic force microscopy, and differential thermal analysis/thermogravimetry analysis. The photocatalytic activity of the thin films was evaluated by the photocatalytic decomposition of acetone in air. The results show that TFA is chemisorbed on the surface of the TiO2 films as a trifluoroacetate complex. The photocatalytic activity of modified TiO2 thin films is higher than that of unmodified TiO2 thin films, and the modified film treated at 250 °C shows the highest activity. This is ascribed to the fact that the TFA complex bound on the surface of TiO2 acts as an electron scavenger and, thus, reduces the recombination of photogenerated electrons and holes....

Preparation and characterization of highly photoactive nanocrystalline TiO2 powders by solvent evaporation-induced crystallization method

Highly photoactive bi-phase nanocrystalline TiO2 photocatalyst was prepared by a solvent evaporation-induced crystallization (SEIC) method, and calcined at different temperatures. The obtained TiO2 photocatalyst was characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results show that solvent evaporation can promote the crystallization and phase transformation of TiO2 at 100℃. When calcination temperatures are below 600℃, the prepared TiO2 powders show bimodal pore size distributions in the mesoporous region. At 700℃, the pore size distributions exhibit monomodal distribution of the inter-aggregated pores due to the collapse of the intra-aggregated pores. At 100℃, the obtained TiO2 photocatalyst by this method shows good photocatalytic activity, and at 400℃, its photocatalytic activity exceeds that of Degussa P25. This may be attributed to the fact that the prepared TiO2 photocatalyst has higher specific surface areas, smaller crystallite size and bimodal pore size distribution.

BASF incorporates sunblocker-grade TiO 2 in nylon fabric

A preliminary optical fiber reactor (OFR) that employs bare quartz fibers as a light-transmitting support of TiO2 was tested for gas treatment by investigating photocatalytic oxidation of acetone in air (50–750 ppmv). Using one or four TiO2-coated fibers in a continuous flow photoreactor, a steady-state conversion up to 80% was achieved at ambient temperature and pressure. The kinetic behavior of the acetone conversion in this study could be described by zero-order kinetics. The characteristics of coated-optical fibers were quantitatively analyzed and their use in photocatalytic gas treatment was discussed in detail. All the acetone molecules degraded was quantitatively converted to CO2 with no intermediates detected. No noticeable deactivation was observed within a few hours’ operation under the present experimental conditions. The conversion of acetone linearly increased with the incident light intensity without showing any sign of saturation. The transmitted light intensity through a TiO2-coated optical fiber exponentially decreased along the fiber, showing 90% extinction within 30 cm. The photocatalytic conversion measured as a function of the coated-fiber length showed a similar trend. An optimal coating thickness was found at around 1.5 μm above which the photocatalytic efficiency was reduced. The presence of water vapor reduced the reactivity due to the competitive adsorption on active surface site with acetone. While a measurable conversion of acetone was observed in the absence of O2, increasing O2 concentration up to 15% effectively enhanced the conversion.

Effects of F- Doping on the Photocatalytic Activity and Microstructures of Nanocrystalline TiO2 Powders

A novel and simple method for preparing highly photoactive nanocrystalline F--doped TiO2 photocatalyst with anatase and brookite phase was developed by hydrolysis of titanium tetraisopropoxide in a mixed NH4F−H2O solution. The prepared F--doped TiO2 powders were characterized by differential thermal analysis-thermogravimetry (DTA-TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV−vis absorption spectroscopy, photoluminescence spectra (PL), transmission electron microscopy (TEM), and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the crystallinity of anatase was improved upon F- doping. Moreover, fluoride ions not only suppressed the formation of brookite phase but also prevented phase transition of anatase to rutile. The F--doped TiO2 samples exhibited stronger absorption in the UV−visible range with a red shift in the band gap transition. The photocatalytic activity of F--doped TiO2 powders prep...

Light-induced super-hydrophilicity and photocatalytic activity of mesoporous TiO 2 thin films

Transparent mesoporous TiO 2 (MTiO 2) and TiO 2 nanometer thin films were prepared on fused quartz via the modified reverse micellar and sol–gel methods. The MTiO 2 and TiO 2 films were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), X-ray diffraction (XRD), BET surface area and UV–Vis spectrophotometry. The photoinduced super-hydrophilicity and photocatalytic activity of the films were evaluated by the water contact angle measurement and photocatalytic oxidation of acetone in air, respectively. It was found that MTiO 2 thin films at 500 °C showed higher photocatalytic activity and better light-induced hydrophilicity than the TiO 2 thin films. This is attributed to the following reasons: (1) MTiO 2 thin films are composed of smaller monodisperse spherical particles about 15 nm diameter, and possess more mesopores between spherical particles and higher surface areas and surface roughness, (2) the monodispersity of MTiO 2 particles was beneficial to the transfer and separation of photo-generated electrons and holes inside of and on the surface of TiO 2 particles, and reduced the recombination of photo-generated electrons and holes. At 900 °C, the MTiO 2 and TiO 2 films appeared to be in the rutile phase, but showed photoinduced hydrophilicity and no photocatalytic activity. This confirmed that the mechanism of photoinduced super-hydrophilicity of the films is different from that of photocatalytic oxidation.

Enhancing effects of water content and ultrasonic irradiation on the photocatalytic activity of nano-sized TiO 2 powders

A simple method for preparing highly photoactive nano-sized TiO 2 photocatalyst with anatase and brookite phase was developed by hydrolysis of titanium tetraisopropoxide in pure water or the EtOH/H 2O mixed solution under ultrasonic irradiation. The prepared TiO 2 powders were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the photocatalytic activity of TiO 2 powders prepared by this method from pure water or the EtOH/H 2O mixed solutions with the molar ratio of EtOH/H 2O=1 exceeded that of Degussa P-25. The molar ratios of EtOH/H 2O obviously influenced the crystallization, crystallite size, BET surface areas and photocatalytic activity of the prepared TiO 2 powders. Ultrasonic irradiation obviously enhanced the photocatalytic activity of TiO 2 powders whether the solvent is pure water or the EtOH/H 2O mixed solutions. This may be ascribed to the fact that ultrasonic irradiation enhances hydrolysis of titanium alkoxide and crystallization of TiO 2 gel.

Rapid synthesis of mesoporous TiO2 with high photocatalytic activity by ultrasound-induced agglomeration

Three-dimensional and thermally stable mesoporous TiO2 was synthesized without the use of any surfactants via treatment with high intensity ultrasound irradiation for a short period of time. Monodispersed TiO2 sol particles were formed initially by ultrasound-assisted hydrolysis of acetic acid-modified titanium isopropoxide. Then, the mesoporous spherical or globular particles, which have a narrow pore size distribution, were produced by controlled condensation and agglomeration of these sol nanoparticles under high intensity ultrasound irradiation. The mesoporous TiO2 was characterized by XRD, TEM, nitrogen adsorption, TGA/DTA and FTIR. Low-angle XRD and TEM show the mesoporous TiO2 has a wormhole-like structure and a lack of long-range order. Nitrogen adsorption results indicate that the mesoporous TiO2 retains mesoporosity with a narrow pore size distribution and high surface area to at least 673 K. The thermal stability of mesoporous TiO2 is attributed to its thick inorganic walls, consisting of TiO2 nanoparticles. TGA study shows that this synthetic method is environmentally friendly. The photocatalytic activity of mesoporous TiO2 for the oxidation of acetone in air was measured. As-prepared mesoporous TiO2 has negligible activity due to its amorphous structure. Calcined mesoporous TiO2 shows better activity than commercial photocatalyst P25. The reasons for the high activity of mesoporous TiO2 are discussed.

Copper-based bioinspired oxygenation and glyoxalase-like reactivity.

Re-engineered, structurally abbreviated models of metalloenzymes may extend their biomimetic functionality to bioinspired reactivity. The oxygenation of external substrates, in particular, remains an important objective of biomimetic and bioinspired catalysis. We report that the reaction of [(Cu(I)TpCF3,CH3)2] with excess acetone in air produces [CuTpCF3,CH3)(lactate)] in over 95% yield at ambient conditions, without any noticeable ligand decomposition. This chemically unprecedented one-pot conversion of acetone to lactate occurs as a multistep process in the gluconeogenic pathway catalyzed by P450 isozyme 3a and Ni- or Zn-based glyoxalases. On the basis of the structure of the [CuTpCF3,CH3)(lactate)] product and oxygenation experiments using isotopically labeled acetone and water, an inner-sphere oxidation/isomerization mechanism is proposed.

Synthesis, Chemistry, and Catalytic Activity of Ruthenium Diaminodiphosphane Complexes − Crystal Structures of trans-[RuCl2{κ3-Ph2PC6H4CH=NC6H10N(H)CH2C6H4PPh2}(PPh3)] and cis-[RuCl2{κ4-Ph2PC6H4CH=NC6H10N(H)CH2C6H4PPh2}

The interaction of [RuCl2(PPh3)3] with one equivalent of N,N′-bis[2-(diphenylphosphanyl)benzyl]-1R,2R-cyclohexanediamine [1R,2R-P(NH)(NH)P] in dichloromethane at room temperature gave trans-[RuCl2{κ3-1R,2R-P(NH)(NH)P}(PPh3)] (1). When heated under reflux in toluene under a nitrogen atmosphere, 1 was converted into trans-[RuCl2{κ4-1R,2R-P(NH)(NH)P}] (2). However, when 1 was stirred at room temperature in air, it was oxidized to trans-[RuCl2{κ3-1R,2R-PN(NH)P}(PPh3)] (3). Depending on the reaction conditions, 3 was converted into trans-[RuCl2{κ3-1R,2R-P(NH)(NH)P=O}(PPh3)] (4) when heated to 80 °C in toluene in air, to cis-[RuCl2{κ4-1R,2R-PN(NH)P}] (5) when stirred at room temperature in acetone in air, or to trans-[RuCl2{κ4-1R,2R-PN(NH)P}] (6) when heated under reflux in acetone under a nitrogen atmosphere. When heated under reflux in toluene under a nitrogen atmosphere, 5 isomerized to 6 quantitatively. When heated under reflux in mesitylene under a nitrogen atmosphere, 6 was slowly reduced to 2. The solid state structures of 3 and 5 were ascertained by X-ray crystallography. Catalytic studies showed that 1 could catalyze the oxidation of alkanes and alkenes with molecular oxygen.

Synthesis, Chemistry, and Catalytic Activity of Ruthenium Diaminodiphosphane Complexes − Crystal Structures oftrans-[RuCl2{κ3-Ph2PC6H4CH=NC6H10N(H)CH2C6H4PPh2}(PPh3)] andcis-[RuCl2{κ4-Ph2PC6H4CH=NC6H10N(H)CH2C6H4PPh2}

The interaction of [RuCl2(PPh3)3] with one equivalent of N,N′-bis[2-(diphenylphosphanyl)benzyl]-1R,2R-cyclohexanediamine [1R,2R-P(NH)(NH)P] in dichloromethane at room temperature gave trans-[RuCl2{κ3-1R,2R-P(NH)(NH)P}(PPh3)] (1). When heated under reflux in toluene under a nitrogen atmosphere, 1 was converted into trans-[RuCl2{κ4-1R,2R-P(NH)(NH)P}] (2). However, when 1 was stirred at room temperature in air, it was oxidized to trans-[RuCl2{κ3-1R,2R-PN(NH)P}(PPh3)] (3). Depending on the reaction conditions, 3 was converted into trans-[RuCl2{κ3-1R,2R-P(NH)(NH)P=O}(PPh3)] (4) when heated to 80 °C in toluene in air, to cis-[RuCl2{κ4-1R,2R-PN(NH)P}] (5) when stirred at room temperature in acetone in air, or to trans-[RuCl2{κ4-1R,2R-PN(NH)P}] (6) when heated under reflux in acetone under a nitrogen atmosphere. When heated under reflux in toluene under a nitrogen atmosphere, 5 isomerized to 6 quantitatively. When heated under reflux in mesitylene under a nitrogen atmosphere, 6 was slowly reduced to 2. The solid state structures of 3 and 5 were ascertained by X-ray crystallography. Catalytic studies showed that 1 could catalyze the oxidation of alkanes and alkenes with molecular oxygen.

Photodissociation of acetone in the troposphere: an algorithm for the quantum yield

Results of recent measurements of quantum yields for the photodissociation of acetone in air are evaluated to derive formulae for the dependence on wavelength and pressure. These are used to calculate acetone photodissociation coefficients in the troposphere. The results are compared to another algorithm suggested previously.

Enhanced photocatalytic activity of mesoporous and ordinary TiO2 thin films by sulfuric acid treatment

Transparent anatase mesoporous TiO2 (MTiO2) and TiO2 nanometer thin films were prepared on soda-lime glass and fused quartz via the reverse micellar method and sol–gel method, respectively. The as-prepared MTiO2 and TiO2 films were then treated by dipping them in a H2SO4 solution. The MTiO2 and TiO2 films before and after surface acid treatment were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), BET surface area and UV–VIS spectrophotometry. The photocatalytic activity of the samples was evaluated by photocatalytic oxidation of acetone in air. It was found that MTiO2 thin films showed higher photocatalytic activity than that of the TiO2 thin films. This was attributed to the fact that MTiO2 thin films were composed of smaller monodisperse spherical particles about 15nm and had higher specific surface areas. Furthermore, the monodispersity of TiO2 particles was beneficial to transfer and separation of photo-generated electrons and holes in the inner of and on the surface of TiO2 particle and reduced the recombination of photo-generated electrons and holes. The films deposited on quartz showed the highest photocatalytic activity because films deposited on quartz exhibited a better crystallization and had no sodium contaminant. The photocatalytic activity of MTiO2 and TiO2 thin films deposited on different substrates after treated with H2SO4 solution was significantly enhanced. Acid treatment was particularly effective for MTiO2/glass and TiO2/glass, which showed activity enhancement of four and over two times, respectively. This increase in activity has been correlated with the reduction of sodium ions and the increase in the adsorbed hydroxyl content on the surface of TiO2 films.

Mu-peroxo-bis[trans-chloro(1,4,8,11-tetraazacyclotetradecane)cobalt(III)] bis(tetraphenylborate) diacetone solvate.

The title complex, [Co(2)Cl(2)(mu-O(2))(cyclam)(2)](C(24)H(20)B)(2).2Me(2)CO, was obtained when [Co(cyclam)Cl(2)](BPh(4))(2) was crystallized from acetone in air; cyclam is 1,4,8,11-tetraazacyclotetradecane, C(10)H(24)N(4). The peroxo O-O moiety straddles a crystallographic centre of inversion (the two octahedral Co atoms are symmetrically bridged by the O(2) moiety), hence only half of the complex cation is in the asymmetric unit. A comparison of the O-O [1.483 (3) A], Co-Cl [2.2647 (8) A] and Co-O [1.894 (2) A] bond lengths with similar bonds in previously determined structures indicates the oxidation of Co(II) to Co(III) during the crystallization process. In the crystal lattice, cation dimers are encapsulated by six [BPh(4)](-) anions, with C-H...pi hydrogen bonds between the cyclam methylene groups and the phenyl rings of the anion.

Investigation on TiO2-coated optical fibers for gas-phase photocatalytic oxidation of acetone

A preliminary optical fiber reactor (OFR) that employs bare quartz fibers as a light-transmitting support of TiO2 was tested for gas treatment by investigating photocatalytic oxidation of acetone in air (50–750ppmv). Using one or four TiO2-coated fibers in a continuous flow photoreactor, a steady-state conversion up to 80% was achieved at ambient temperature and pressure. The kinetic behavior of the acetone conversion in this study could be described by zero-order kinetics. The characteristics of coated-optical fibers were quantitatively analyzed and their use in photocatalytic gas treatment was discussed in detail. All the acetone molecules degraded was quantitatively converted to CO2 with no intermediates detected. No noticeable deactivation was observed within a few hours’ operation under the present experimental conditions. The conversion of acetone linearly increased with the incident light intensity without showing any sign of saturation. The transmitted light intensity through a TiO2-coated optical fiber exponentially decreased along the fiber, showing 90% extinction within 30cm. The photocatalytic conversion measured as a function of the coated-fiber length showed a similar trend. An optimal coating thickness was found at around 1.5μm above which the photocatalytic efficiency was reduced. The presence of water vapor reduced the reactivity due to the competitive adsorption on active surface site with acetone. While a measurable conversion of acetone was observed in the absence of O2, increasing O2 concentration up to 15% effectively enhanced the conversion.

Photodissociation of Acetone in Air: Dependence on Pressure and Wavelength. Behavior of the Excited Singlet State

Quantum yields of acetyl radicals resulting from the photodissociation of 0.1−1% acetone in air were studied in the wavelength range 280−330 nm and at total pressures ranging from 130 to 1000 hPa. Through the addition of small amounts of NO2 to the gas mixtures, acetyl peroxy radicals were scavenged to form peroxyacetyl nitrate (PAN). The PAN quantum yields obeyed a Stern−Volmer type pressure dependence at all wavelengths studied. The experimental data were combined with results from the literature to derive the rate of photodissociation from the excited singlet state of acetone and the competing intersystem crossing rate populating the triplet state, both relative to that of pressure quenching, as a function of energy above the dissociation threshold. The rate of photodissociation was found to increase with excitation energy, whereas that of intersystem crossing shows a maximum at intermediate energies. Previously reported quantum yields for CO formation were analyzed to allow comparison with acetyl radical production.

Influence of Thermal Treatment on the Adsorption of Oxygen and Photocatalytic Activity of TiO2

Thermal treatment in air has a marked influence on the adsorption of oxygen and the photocatalytic activities of TiO2 (P25) for the oxidation of acetone in air. The photoactivity of TiO2 increases ...

A screening level examination of the potential risks of acetone in aquatic and terrestrial environments using multi-media modeling

Approximately half of the ∼40 million tonnes per annum (t/a) of acetone released worldwide arises via natural processes. The remaining releases of acetone are the focus of this assessment and arise either as a photo-degradation by-product of other organic compounds (∼20 million t/a) or by entering the environment from manufacturing and end uses (59,000 t/a). Multi-media modeling was used to estimate regional concentrations of acetone in air, water, soil and sediment that may occur based on these anthropogenic releases to the environment. US toxics release inventory data were used to calculate local surface water concentrations. The distributions of all regional and local concentrations in all media were below applicable predicted no effect concentrations (PNECs). Calculated regional and local concentrations of acetone, originating from all anthropogenic sources, appear unlikely to cause adverse risks to the environment.